Effects of fabrication method on defects induced by nitrogen diffusion to the hafnium oxide layer in metal–oxide–semiconductor field effect transistors

This study investigates how different metal gate fabrication methods induce variations in the defects which result from nitrogen diffusing into the hafnium oxide layer in metal–oxide–semiconductor field effect transistors (MOSFETs). By using the different fabrication methods of pre-TaN, post-TaN and post-TiN annealing, the work-function difference between the gate material and the semiconductor can be adjusted, leading to apparent differences in threshold voltage (Vth). In addition, the results of slow and fast I–V NBTI measurements show that the amount of the bulk trapping in the post-TiN device is the highest, followed by the post-TaN device and then the pre-TaN device. In addition, a nitrogen interstitial defect phenomenon, resulting in a temporary shift of threshold voltage (Vth) which is highest in the post-TiN the lowest in the pre-TaN device, is determined by double sweep fast I–V measurements.